United States
Environmental Protection
Agency
Risk Reduction
Engineering Laboratory
Cincinnati, OH 45268
Research and Development
EPA/600/SR-94/063 May 1994
EPA Project Suimmary
Wash Solvent Reuse in Paint
Production
Alice B. Parsons, Kenneth J. Heater, and Robert F. Olfenbuttel
This project evaluated solvent used
to clean paint manufacture equipment
for its utility in production of subse-
quent batches of solvent-borne paint.
Reusing wash solvent would reduce
the amount of solvent disposed of as
waste. The evaluation of this wash-sol-
vent recovery technology was con-
ducted by Battelle Memorial Institute
for the Pollution Prevention Research
Branch of the U.S. Environmental Pro-
tection Agency. The evaluation was
conducted with the cooperation and
assistance of Vanex Color, Inc.
The product quality, waste reduction/
pollution prevention, and economic im-
pacts of this technology change, as it
has been implemented by Vanex, were
examined. Two batches of a solvent-
borne alkyd house paint were prepared
at Vanex—one batch made with 100%-
new solvent and the other with 80%-
wash solvent—and sampled for
laboratory analysis at Battelle. Product
quality was evaluated by Battelle ac-
cording to appropriate ASTM Itest meth-
ods and by Vanex quality-control
personnel according to normal produc-
tion procedures. Waste reduction and
economics were documented from
company records and interviews with
key company personnel. The technol-
ogy was found to reduce waste and
operating costs without affecting prod-
uct quality.
This Project Summary was developed
by the EPA's Risk Reduction Engineer-
ing Laboratory, Cincinnati, OH, to an-
nounce key findings of the research
project that is fully documented in a
separate report of the same title (see
Project Report ordering information at
back).
Introduction
The Pollution Prevention Research
Branch (PPRB) of the U.S. Environmental
Protection Agency is evaluating and dem-
onstrating pollution prevention technolo-
gies through the Pollution Prevention Clean
Technology Demonstration (CTD) Pro-
gram. The CTD program focuses on tech-
nologies that can be used within a
particular industry to minimize the source
of pollution problems. This study, con-
ducted by Battelle, evaluated a technol-
ogy for reducing solvent waste by reusing
wash solvent in the manufacture of paint.
The solvent used to clean equipment at
the end of a production run is stored for
use in the next formulation of the same
type of paint.
Three aspects of this technology were
evaluated: product quality, pollution pre-
vention, and economics. The goal of this
solvent reuse study was to evaluate (1)
the quality of the paint formulated with
wash solvent to ensure that product qual-
ity has not been compromised, (2) the
amount of solvent diverted from the
wastestream by this technology, and (3)
the cost to operate this pollution preven-
tion program.
The site selected for evaluation of this
technology was Vanex Color, Inc., located
in Mt. Vernon, IL. Small amounts of sol-
vent are used to clean the batch tanks
and the dispensing equipment. Vanex
stores mineral spirits used to clean mixing
and dispensing equipment after produc-
Printed on Recycled Paper
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tion of each batch of paint and reuses this
wash solvent as part or all of the solvent
needed to manufacture subsequent
batches of solvent-borne paint. The per-
centage of reused solvent varies from
batch to batch and depends on the amount
of stored solvent available at the time of
production.
Only certain coatings are formulated with
the stored wash solvents. Product lines
selected by Vanex for its solvent reuse
program were primarily those that could
be easily formulated to meet final color
requirements. The Vanex technical staff
put together a master list of wash sol-
vents and paints that could be formulated
with the wash solvents, based on the
chemistry of the polymers, the color of the
pigments, and the gloss required in the
paint being mixed. Wash solvents (min-
eral spirits) stored for reuse are assigned
to storage drums in one of three solvent
recovery groups.
Solvent is stored in labeled 55-gal drums
for addition back into the same or very
similar paint formulations within 90 days.
During the first 24 hr of storage, pigment
settles out of the wash solvent and col-
lects at the bottom of the drum. There-
fore, when solvent is removed from the
drum to be added to a production batch,
care Is taken to ensure that none of the
sediment (mostly pigments) in the bottom
of the drum is added to the formulation.
Solvents not selected for reuse are col-
lected In drums and shipped to,a solvent
blender who processes and sells the mixed
solvent to a cement kiln as a fuel additive.
Results and Discussions
Product Quality Evaluation
The paint formulated with wash solvent
should meet the same product specifica-
tions established by Vanex for paint for-
mulated with 100%-new solvent. For this
study, two batches of a solvent-borne alkyd
house paint were prepared at Vanex, un-
der the observation of the Battelle Labo-
ratory Manager conducting this study. One
batch was formulated with 100%-new sol-
vent and the other with 80%-wash sol-
vent. Vanex personnel ran their standard
quality-control tests on each batch, and
field samples were collected by Battelle
for further laboratory analysis. The same
series of standard analytical tests was run
on each batch.
Vanex quality assurance personnel
evaluated samples in the field after the
initial formulation and after a 16- to 24-hr
holding period. The paint formulated with
80%-wash solvent compared well with the
paint formulated with 100%-new solvent.
Table 1 shows the Vanex quality-control
test results for both batches of coatings.
The paint made with wash solvent re-
quired no adjustments to meet the ex-
pected ranges. The paint formulated with
100%-new solvent required the addition
of 2 gal of mineral spirits to bring the final
viscosity from 91 Krebs units to 89 units.
Vanex rated these two batches of alkyd
house paint as comparable in quality be-
cause quality-control data for the two
batches indicated a close match for the
tested parameters. The company's qual-
ity-control procedures use a visual match
of wet color. The color of a coating batch
being mixed is checked against a stored
color standard by visual comparison of
wet side-by-side drawdowns of the batch
and the appropriate color standard. The
Vanex quality-control staff judged the wet
color of both of the batches prepared and
sampled for this study to match the color
standard without adjustment.
Further laboratory analysis at Battelle
of the field samples collected during the
site visit supported this conclusion. The
tests used at Battelle and the test results
are listed in Table 2. The gloss of the
wash-solvent batch tested slightly higher
than that of the new-solvent batch, but not
statistically different. The average percent
solids for the coating batch manufactured
with new solvent was 26.6%; the percent
volatiles, 73.4%. The average percent sol-
ids for the batch manufactured with wash
solvent was 26.5%; the percent volatiles,
73.5%. The results of the percent solids/
percent volatiles determination show that
the use of wash solvent did not affect the
solids and volatiles content of the paint
formulated. The viscosity determination
also revealed no difference between the
batch manufactured with wash solvent and
the one formulated with new solvent. The
instrumental measurement of dry film color
as color difference (AE) calculated by the
CIELAB formula indicated no significant
difference in color between the batch made
with 100%-new solvent and the batch
made with 80%-wash solvent.
Tablo 1, Results of Quality-Control Tests for Product Quality Assessment Performed at Vanex
Property (Units) Test Method' Vanex Range* New-Solvent Batch
Wash-Solvent Batch
Viscosity (Krebs Units)
Density (Jo/gal)
(g/ml)
Grind (Hegman Scale)
Unear flow (sag)
Color
Gloss (gloss units)
ASTM D562-81 (reapproved 1990) 88±2
ASTM D1475-90 10.36±0.05
(1.24± 0.0)
ASTM D1210-79 >5
(reapproved 1988)
ASTM D4400-89a 12
Visual comparison with Match stored
stored standard standard
ASTMDS23-89 (60°) >80
89
10.37
(1.24)
6+
12
yes
87.1
89
10.40
(1.25)
5+
12
yes
86.6
' American Society for Testing and Materials, 1992 Annual Book of ASTM Standards, Vol. 06.01, "Paint -
Tests for Formulated Products and Applied Coatings."
t Approved range for Vanex #2-1 alkyd housepaint.
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Table 2. Results of Tests for Product Quality Assessment Performed at Battelle
Property (Units)
Viscosity (Cent/poises)
Density (Ib/gal)
Grind (Hegman Scale)
Percent Solids (%)
Percent Volatiles (%)
Color (A E) CIELAB
Gloss (gloss units)
Test Method*
ASTMD2196-86
(reapproved 1991)
ASTMD1 475-90
ASTMD1210-79
(reapproved 1988)
ASTMD2369-90
ASTMD2369-90
ASTMD2244-89
ASTMD523-89
New-Solvent batch
4000
data not valid
8
73.4
26.6
Standard for Comparison
79.4
Wash-Solvent Batch
4000
data not valid
8
73.5
26.5
0.2
81.6
"American Society for Testing and Materials, 1992 Annual Book of ASTM Standards, Vol. 06.01,
"Paint —Tests for Formulated Products and Applied Coatings."
Employees at Vanex make a conscious
effort to minimize the amount of solvent
required for cleaning by techniques such
as physical scraping of the mix tanks to
remove many paint solids before solvent
cleaning. Workers minimize the need for
cleanup of work areas and equipment by
taking care when adding raw materials
and dispensing finished batches. They ar-
range production schedules so that, when-
ever possible, similar batches of paint are
mixed and dispensed one after another to
eliminate cleanup between batches.
The volume of wash solvent diverted
from the wastestream could vary from year
to year, depending on the product mix
and the annual production. This low-tech
system has, however, produced an ap-
preciable reduction in solvent waste at
Vanex. Production figures and background
information collected during two site visits
to Vanex (Table 3) indicate that, in 1992,
Vanex diverted about 3,300 gal (12,500
The sample size was limited to two
batches of paint, but the quality-control
tests at Vanex and the laboratory analysis
at Battelle indicate that the quality of the
solvent-borne alkyd house paint made with
wash solvent is comparable with that of
the product quality of the same paint made
with 100%-new solvent. These results
compare well with the experience that
Vanex has accumulated during the sev-
eral years it has used this wash-solvent
recovery system.
Pollution Prevention Potential
Waste is reduced in two ways when
this technology is practiced as at Vanex
for manufacture of solvent-borne paints:
(1) disposal of wash solvent is reduced
and (2) solvent purchase for paint manu-
facture is reduced. In addition, the use of
this technology did not increase other types
of pollution. '• '
Solvent required to clean the mixing
and dispensing equipment .between
batches is the major source of solvent
waste in the manufacture of solvent-borne
paint. Information from company records
and from interviews with key staff was
gathered to determine the volume of wash
solvent (mineral spirits) diverted from the
wastestream by implementation of the re-
use program at Vanex.
Table 3. Annual Waste Reduction Through Wash-Solvent Reuse Program at Vanex Color, Inc.
Vanex Production Data:
Production in 1992 of solvent-borne paints:
Average batch size
Estimated number of batches/year:
Quantity of mineral spirits used to clean
tanks and equipment between batches:
Wash Solvent Calculations:
Without Reuse
Solvent required for cleanup only
(206 batches X20 gal/batch)
Wash solvent disposed
With Reuse
Solvent required for cleaning only
(206 batches X 20 gal/batch)
Solvent reused for formulation
(80% X 4,120 gal)
Wash solvent disposed
Waste Reduction
82,500 gal (312,000 L)
400 gal (1,500 L)
206 batches
20 gal (75 L)
4,120 gal (15,600 L)
4,120 gal (15,600 L)
4,120 gal (15,600 L)
3,300 gal (12,500 L)
820 gal (3,100 L)
3,300 gal (12,500 L)
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ume of solvent waste requiring disposal
from 13.6 million gal to 2.7 million gal, a
reduction of 10.9 million gal.
Economic Evaluation
The objective of the economic estima-
tion was to calculate a payback period
and/or cost reduction associated with
implementation of this technology for re-
ducing the solvent wastestream. Imple-
mentation of the wash-solvent reuse
system at Vanex did not have significant
capital costs. No equipment was pur-
chased, no additional storage area was
needed, and no additional energy- or air-
supply systems were required. Vanex per-
sonnel estimate the total cost (materials
and labor) of establishing the solvent-re-
use system at less than $1,000.
Because the reuse program has reduced
substantially the quantities of solvent that
must be purchased and disposed of,
Vanex estimates that it saves $15,000
annually in raw material purchases and
disposal costs. For this economic evalua-
tion, Battelle used a conservative estimate
of $11,600 for 1992 savings. Other oper-
ating costs have not been affected. Labor
costs for handling wash solvent are the
same whether the solvent is disposed of
or stored for reuse, and drums to collect
Estimate of Annual Waste Reduction if Wash Solvent Reuse Implemented
Throughout the U.S.
L) of mineral spirits (60 drums/year) from
the wastestream to product formulation.
This represented an 80% reduction In min-
eral spirits disposed of as waste that year.
Interim storage of wash solvent for re-
use at Vanex does not create an addi-
tional source of pollution. Wash solvent is
stored in closed barrels in the same way
that waste solvent is stored to await dis-
posal. The maximum storage on-site for
any waste is 90 days. At Vanex, produc-
tion batches are planned such that stored
solvent is used in less than 90 days.
Using the Vanex solvent recovery rate
and U.S. production figures for solvent-
boms coatings, ft is possible to estimate
the effect that adoption of this technology
could have on wash-solvent waste reduc-
tion each year in the U.S. (Table 4). Ac-
cording to U.S. Department of Commerce
figures, production of paints in the U.S. in
1992 was 1.10 billion gal. Industry figures
suggest that about 62% of this volume
(682 million gal) was solvent-borne coat-
ings in 1992, although the percentage has
been falling each year.
Equipment cleaning in production of 682
million gal of solvent-borne paint cbuld
generate as much as 13.6 million gal "of
waste wash solvent. Recovery of 80% of
this wash solvent could reduce the vol-
Assumptions Based on Industry Data:
Annual production of solvent-borne paints:
Estimated number of batches @ 1,000 gal/batch:
Quantit/ of mineral spirits used to clean
tanks and equipment between batches:
Wash Solvent Reduction Calculations:
682 million gal
(2,580 million L)
682,000 batches
20 gal/batch
(75 L)
Without Rouse
Solvent required for cleanup only
(682,000 batches X 20 gal/batch)
Wash solvent disposed
With 80% Reuse
Solvent required for cleanup
(682,000 batches X 20 gal/batch)
Solvent reused for formulation
(80% X 13.6 million gal)
Wash solvent disposed
(13.6 -10.9 million gal)
Waste Reduction
13.6 million gal
(51. 5 million L)
13.6 million gal
(51. 5 million L)
13.6 million gal
(51. 5 million L)
10.9 million gal
(41. 3 million L)
2.7 million gal
(10.2 million L)
10.9 million gal
(41. 3 million L)
the solvent are required in either case.
Labor costs for adding the stored wash
solvent to the paint formulation do not add
significant cost to the mixing operation.
Using the cost of implementation and
the savings resulting from decreased waste
of solvent, the payback period for imple-
mentation of the wash-solvent recovery
system at Vanex was found to have been
approximately one month.
Payback = $1.000
$11,600
Payback ~ one month
Savings for other companies instituting
similar systems will vary with production
volumes and the volume of wash solvent
recovered from the wastestream.
Conclusions and
Recommendations
The major source of solvent waste in
paint manufacture is wash solvent used to
clean tanks and equipment. The very sim-
plicity of this technology makes it desir-
able for paint companies actively pursuing
reduction of solvent waste. It is especially
useful for small-to-medium companies
manufacturing several solvent-borne paints
in small production batches.
The quality-control tesrts at Vanex and
the laboratory analyses at Battelle indi-
cate that the product quality of a batch of
solvent-borne alkyd house paint made with
a formulation in which 80% of the solvent
had been recovered from equipment-clean-
ing operations was comparable to that of
a batch made with 100%-new solvent. All
Vanex products must meet specific qual-
ity-control standards. The experience that
Vanex has accumulated while using this
wash-solvent recovery system for several
years is that paint formulated with se-
lected wash solvent meets its quality as-
surance standards and those of its
customers.
Reusing wash solvent in the subsequent
formulation of coating products (1) reduces
the amount of wash solvent that must be
disposed of as waste and (2) reduces the
amount of solvent that must be purchased
for use in paint formulations. Interim stor-
age of the wash solvent before reuse does
not contribute to additional pollution. Vanex
is able to reuse about 3,300 gal of min-
eral-spirits wash solvent per year.
The payback period for implementation
of the wash-solvent recovery system at
Vanex was about one month. Vanex has
estimated yearly savings through the wash
solvent recovery system at $15,000;
Battelle's conservative estimate of yearly
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savings was $11,600 per year based on
Vanex's figures for 1992. Capital costs in
the first year were estimated at less than
$1,000.
The results of this evaluation suggest
that the wash-solvent recovery system can
be used by manufacturers of solvent-borne
paint to reduce the volume of solvent waste
without affecting product quality, as well
as positively impacting the environment.
Sound experience and knowledge of the
chemistry of the paint formulations is
needed to plan a reuse protocol for a
particular facility. This technology system
can produce cost savings with little capital
outlay for implementation and little or no
increase in operating expenses.
Acknowledgments
The U.S. EPA and Battelle acknowl-
edge the cooperation and support of the
technical and administrative staff of Vanex
Color, Inc., during the technology evalua-
tion process. Ken Brandt and Walter
Rexing provided technical information and
assistance with production scheduling that
made the program possible.
*U.S. GOVERNMENT HUNTING OFFICE; I»M - S5
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Alice B. Parsons, Kenneth J. Heater, and Robert F. Olfenbuttel are with
Battelle, Columbus, OH 43201.
Lisa Brown is the EPA Project Officer (see below).
The complete report, entitled'Wash Solvent Reuse in Paint Production," (Order
No. PB94-161130; Cosl;$17.50, subject to change) will be available only
from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Risk Reduction Engineering Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
United States
Environmental Protection Agency
Center for Environmental Research Information
Cincinnati, OH 45268
Official Business
Penalty for Private Use
$300
BULK RATE
POSTAGE & FEES PAID
EPA
PERMIT No. G-35
EPA/600/SR-94/063
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